GtkCallback

void
(* GtkCallback) (
  GtkWidget* widget,
  gpointer data
)

The type of the callback functions used for e.g. iterating over the children of a container, see gtk_container_foreach().

`widget`	`GtkWidget`
	The widget to operate on.
	The data is owned by the caller of the function.
`data`	`gpointer`
	User-supplied data.